Extended Data Fig. 7: Comparison of the CO₂ effect size (%) and the associated confidence intervals for major (a) plant (b) soil, and (c) operationally-defined soil phosphorus (P) pool variables, calculated by the original approach as reported in the main text (Original) and a bootstrapping method (Bootstrap, Supplementary Information 2.2).

(a) The CO₂ effects on plant P pools, including canopy, sapwood, heartwood, total wood, fine root, coarse root, forest floor leaf litter, understorey and, understorey litter; (b) the CO₂ effects on soil P pools, including microbes, labile soil P and total soil P pools in the 0���10 cm, 10–30 cm, and 30–60 cm depths, respectively; (c) the CO₂ effect on soil P pools in the top 10 cm of the soil, classified based on the Hedley fractionation method, including exchangeable inorganic P (P_i), exchangeable organic P (P_o), moderately labile P_o, and occluded P, which is the remaining P that we consider to be relatively unavailable to plants. Values indicate the mean absolute CO₂ effect, calculated by using elevated minus ambient CO₂ treatment (n = 3), with the coloured bars indicating confidence intervals at 95%, 85% and 75% (two-tailed t-test, with lighter colours indicating higher confidence levels).